Omental and Subcutaneous Adipose Tissues of Obese Subjects Release Interleukin-6: Depot Difference and Regulation by Glucocorticoid

The purpose of this study was to determine whether human adipocytes from different depots of obese subjects produce interleukin-6 (IL-6) and whether IL-6 release is regulated by glucocorticoids. Fragments of omental and abdominal sc adipose tissue released immunodetectable IL-6 into the medium during acute incubations. Omental adipose tissue released 2-3 times more IL-6 than did sc adipose tissue. Isolated adipocytes prepared from these tissues also released IL-6 (omental > sc), but this accounted for only 10% of the total tissue release. Culture of adipose tissue fragments for 7 days with the glucocorticoid dexamethasone markedly suppressed IL-6 production. These data show for the first time that substantial quantities of IL-6 (up to 75 ng/mL) accumulate in the medium during incubations of both adipocytes and adipose tissue. Although little is known about the effects of IL-6 on adipose tissue, one action is a down-regulation of adipose tissue lipoprotein lipase. The regulated production of this multifunctional cytokine may modulate regional adipose tissue metabolism and may contribute to the recently reported correlation between serum IL-6 and the level of obesity.